Every point of armor requires a unit to take 1% more of its maximum health in physical damage to be killed. This is called effective health.

Example: A unit with 60 armor has 60% more of its maximum health in effective health, so if the unit has 1000 maximum health, it will take 1600 physical damage to kill it.

What this means: by definition, armor does not have diminishing returns, because each point increases the unit's effective health against physical damage by 1% of its current actual health whether the unit has 10 armor or 1000 armor.

Note: Unlike health, increasing armor also makes healing more effective because it takes more effort to remove the unit's health than it does to restore it.

格雷福斯的True GritTrue Grit increases his armor by 1 / 2 / 3 every second he remains in combat. This bonus stacks up to 10 times. Graves is considered in combat if he has dealt or received damage in the last 3 seconds.

嘉文四世的Demacian Standard passively increases his armor by 10 / 13 / 16 / 19 / 22. When activated it throws a flag to a target location that grants the passive benefit to nearby allies and to himself again.

蕾欧娜的Eclipse increases her armor by 30 / 40 / 50 / 60 / 70 for 3 seconds, deals damage after that time to units around her, and retains the defensive buff for an additional 3 seconds if any enemy is struck by the blast.

波比的Paragon of DemaciaParagon of Demacia increases her armor by 1.5 / 2 / 2.5 / 3 / 3.5 for 5 seconds upon attacking or being hit by an enemy, stacks up to 10 times. She can also activate this ability to gain max stacks.

塔里克的Shatter passively increases his armor by 10 / 15 / 20 / 25 / 30 while the ability is not on cooldown and grants himself and nearby allied units' the same bonus again as a permanent aura.

特朗德尔的Agony targets an enemy to steal their armor by 15% / 20% / 25%. This amount is doubled over the next 6 seconds. Trundle increases his own armor by the same flat amount as the armor they enemy lost.